[pilom]

Being a little loose with my estimates and a bit of Fermi Math, thats only about 300 years of computing time on a small home built GPU cluster.

Basically tells me that 4 random words are definitely crackable and 5 are theoretically possible (and definitely doable with 5-10 years of Moore's law)

[dllthomas]

lg(65k^4) is very nearly 64. If you worry about 4 random words being brute forced, you should worry about 64 bit symmetric keys being brute forced. I don't know where the current recommendations come down on that.